Astronomik H-alpha 6nm

The Astronomik 6nm H-alpha filter is an extremely narrow emission-line filter for CCD photography. The filter lets the H-alpha light of emission nebulae pass and blocks nearly the whole remainder of the spectrum where the CCD is sensitive.

We have re-desgined all of our photographic filters. Since the end of 2008 we are shipping our new "Halo-Free" filters. read more...

The full width at half-maximum (FWHM) of 6nm is optimized for a maximum contrast between the (H-alpha emitting) object and the background. The contrast gain is much higher than with our 12nm emission line filters but you won’t see as much stars in the resulting images.

The design of the transmission curve makes it possible to use the filters with instruments from 1:3.75 to 1:15. Selected filters for faster system are available upon special request.

The Astronomik 6nm H-Alpha filter is offered in three qualities: B, A and A+. Filters with a maximum transmission of 80%-85% are class B, 85%-90% are class A, and filters with a transmission of more than 90% are class A+.

All transmission curves of the 6nm filter are measured individually. Because of this procedure you can get the optimum filter for your telescope: If you place a direct order please specify the focal ratio of your instrument and we will select the best filter for your setup. So you may get the best filter without paying for an A+ filter.

Main use

The Astronomik H-alpha-CCD (6nm version) increases the contrast between objects, in this case between the H-alpha emission line and the skyglow background in the same way as the 12nm version. The gain in contrast is much higher due to the smaller FWHM. The 6nm H-Alpha filter is the right choice for extremely dim objects, even in the milkyway, and for observations from heavily light-polluted places. The Astronomik 6nm H-alpha-CCD completely suppresses the emission lines of artificial lighting (mercury (Hg) and sodium (Na)) and skyglow. Transmission losses and chromatic distortions, which arise with other filters, only occur with Astronomik filters when extremely bright aperture ratios come into play. Selected filters for faster systems are available upon special request.

Other uses

Using the Astronomik 6nm H-Alpha together with the 12nm H-Alpha gives you the ability to have a maximum contrast in the HII objects and to keep the stars in the final image.
The Astronomik 6nm H-Alpha filter may NOT be used for solar observation.

Alternatives

If you plan to do (false-)color imaging with other emission line filters, you should get our matching filters with 12nm FWHM. Images taken with filters with differing FWHM are very difficult to combine into the final image.

Suitability

Visual observation (dark skies): Unsuitable
Visual observation (urban skies): Unsuitable
Film photography: Unsuitable
CCD photography: Very good, huge contrast enhancement at H II-emission nebulas
DSLR photography (original): Good, reduced sensitivity in the H-alpha band
DSLR photography (astro modified): Very good, huge contrast enhancement at H II-emission nebulas
DSLR photography (MC modified): Very good, huge contrast enhancement at H II-emission nebulas
Webcam / Video (Planets): Unsuitable
Webcam / Video (Deep Sky): Unsuitable

Technical Data

Parfocal with other Astronomik filters
Glass thickness: 1mm
Completely resistant against high humidity, scratches and aging effects
Diffraction limited, the filter will not reduce the optical performance of your telescope!
Astronomik filters are delivered in a high-quality, long lasting, filter box